The present invention relates to sample collection of particles, particularly to the collection and concentration of small (1-10 xcexcm) respirable particles for analysis, and more particularly to a low power, man-portable apparatus to capture and concentrate small respirable particles into a sub-milliliter volume of fluid for analysis.
Substantial development work has been done in recent years on portable Polymerase Chain Reaction (PCR) and cytometric detectors with the ultimate goal of producing man-portable biological agent detection systems. At the front end of these systems is a sample collector, which collects and concentrates the agents of interest into a liquid sample volume. The agents sampled are generally in the form of respirable particles with sizes in the range of 1-10 xcexcm.
The sample collectors now used with mini PCRs and mini-flow cytometers are large (typically several liters in volume), requiring relatively large fans which draw too much power for portable use. These prior collectors concentrate their sample into milliliter (mL) size volumes, and are inefficient for low-concentration samples. Detectors and their associated sample volumes are becoming smaller ( less than 100 xcexcL for PCR), so currently available mL sample volumes are much too large. A recent approach to a small sample collector is described in xe2x80x9cA Portable High-Throughout Liquid-Absorption Air Sampler for Respirable Aerosol Particlesxe2x80x9d, A. Birenzvige et al, Aerosol Science and Technology, 29: 133-140 (1998). In this approach, a liquid extractant was injected into a conical cavity and a fan was then activated so as to draw air into the cavity, whereby the highly turbulent and swirling motion of the air caused the liquid to swirl up and wet the wall of the sampling tube such that particles in the air collected in the liquid, and after a few minutes the fan was shut off and the liquid drained for analysis. While the above described sample collector reduced the sample volume size, the collection apparatus is complex, expensive, and has low efficiency.
An ideal sample collector, for aerosol liquids, airborne pathogens, or other small particles of interest, should be low power, man-portable, inexpensive, and can concentrate the sample into a volume less than 100 xcexcL. The present invention provides a solution to the above reference need for a small volume sample collector, and involves an apparatus and method to capture and concentrate small (1-10 xcexcm) respirable particles into a sub-milliliter volume of fluid, and thus provides a sample collector wherein the fluid volume with concentrated particles is small and compatible with current mini-PCRs and mini-flow cytometers. The method of the invention is of a two step, or phase operation, inspiration and concentration, where the inspiration step basically collects particles on a wetted wall having small slits therein that act as capillary channels, and the concentration step basically involves spinning the wetted wall to drive the particles and fluid through the small slits and such impinge on a non-wetted surface and slide off into a container. The basic difference in this apparatus and methods from previous approaches is that the collection phase uses a fixed volume defined by the capillary slits, and the amount of particles collected in the concentration phase is determined by the sampling time.
It is an object of the present invention to provide a small volume sample collector.
A further object of the invention is to provide a small volume, low power, man-portable sample collector for small particles of interest.
A further object of the invention is to provide for the capture and concentration of 1-10 xcexcm size respirable particles into a sub-milliliter volume of fluid.
Another object of the invention is to provide a two phase method of collecting and concentrating small particles into a small volume fluid sample.
Another object of the invention is to provide a sample collector having wetted capillary channels, and a concentrator that forces the collected particle by centrifugal force through the capillary channels into a container.
Another object of the invention is to provide a man-portable, small fluid volume, sample collector and concentrator for 1-10 xcexcm size particles of interest that is compatible with mini-PCRs or mini-flow cytometers.
Another object of the invention is to provide a man-portable, small fluid volume particle collector and concentrator wherein the collection phase uses a fixed volume, defined by capillary slits, and the concentration phase is determined by the sampling time.
Other objects and advantages of the present invention will become apparent from the following description and accompanying drawings. Basically the invention involves a low power, man-portable, small fluid volume sample collector for 1-10 xcexcm size aerosol liquids, airborne pathogens, or other small particles of interest. The invention involves an apparatus and method to capture and concentrate small (1-10 xcexcm) respirable particles into a sub-milliliter volume of fluid. The method is a two step or phase operation involving first collection and second concentration. The collection (inspiration) phase involves a cylindrical liner with small vertical slits that act as capillary channels connected to a fluid reservoir and provide a wetted surface to trap particles present in air being blown through the cylindrical liner. The concentration phase involves a transfer operation wherein the cylindrical liner is spun and the collected sample volume is forced through the capillary channels and against a non-wetted surface that deflects the sample to the bottom of the device where it is collected. The collection phase uses a fixed volume, defined by the capillary slits, and the concentration is determined by the sampling time. Thus, to get a higher concentration of particles into the sample, the inspiration step is longer, but the sample size stays the same.